Currently the Sirius binary star system is moving towards the Sun at 5.5km/s for roughly the next 60 thousand years or so. At the end of those years it will be 7.8 light years away from the Sun and roughly 6.8 light years away from the Kuiper belt with a magnitude of 1.64.

So at what point will these two massive stellar objects (in addition to objects orbiting around them adding to their masses too) start to affect the Kuiper belt and trigger frozen objects to start moving through the solar system and potentially cause another extinction level event? What effect do these objects (Sirius A. and B.) have on the Kuiper belt? Will they begin to push and pull on all the other objects in the Kuiper belt and cause them to collide and send them on unknown trajectories? Will it be during the next 60 thousands years that the Sirius binary system is advancing towards the Sun?

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    $\begingroup$ Welcome to Astronomy Stack Exchange! Yes it seems that the radial velocity of Sirius is indeed −5.50 km/s and if that was the only component of its velocity, it might indeed get quite close in about 500,000 years. But that's only one of three components of its velocity. Hopefully someone will take a look at its distance and proper motion and estimate how much sideways velocity it also has. My guess is that it's not really coming directly towards us. $\endgroup$
    – uhoh
    Commented Jul 24, 2022 at 5:06
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    $\begingroup$ different but related: When will Sirius be closest to the solar system? and How often do stars pass close (~1ly) to the Sun? $\endgroup$
    – uhoh
    Commented Jul 24, 2022 at 20:37
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    $\begingroup$ Why are you asking about the Kuiper belt? Do you mean the Oort cloud? en.wikipedia.org/wiki/Oort_cloud $\endgroup$
    – PM 2Ring
    Commented Jul 25, 2022 at 6:22

1 Answer 1


Probably never.

It will make its closest approach in about 64,000 years at a distance of about 7.86 light years. That's not a huge difference from its current distance of about 8.7 light years.

I'm basing this on a graph on Wikipedia's page of the List of nearest stars and brown dwarfs which also indicates ("Sirius" label in the upper right corner) that while the radial velocity is -5.5 km/s the total speed of the star relative to our solar system is about 33 km/s; so the primary velocity component is perpendicular to our line of sight. It's not really coming towards us very fast.

Stars near to the Sun (up to 10 Lightyears) from -20000 to +80000 Years https://commons.wikimedia.org/wiki/File:NearSunStarsSimple.jpg

Stars near to the Sun (up to 10 Lightyears) from -20000 to +80000 Years



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